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The grains in sandstone vary in size from coarse particles, which are up to 1 millimeter in diameter, to fine sand with widths of 0.0625 millimeters. The primary material in sandstone is quartz, followed by feldspar. The formation of sandstone begins as water or wind carries away bits of eroding rocks. When the wind or water loses energy and is unable to carry them any farther, the particles are dumped in a process called "sedimentation."